JH

Chapter 1: Motherboards, Processors, and Memory - Vocabulary

Motherboard Form Factors

  • ATX (Advanced Technology eXtended)- Full-size desktop board (approximately 12 \text{ in} \times 9.6 \text{ in} or 305 \text{ mm} \times 244 \text{ mm})

    • Designed for optimal airflow and component placement

    • Plenty of RAM slots (typically 4-8), up to 7 expansion slots (PCIe x16, x8, x4, x1)

    • Native 24-pin ATX power connector and separate 4/8-pin EPS 12V CPU connector for stable power delivery

    • Common in high-performance gaming, workstation, and enthusiast builds due to expandability

  • Micro-ATX- Shortened ATX (approximately 9.6 \text{ in} \times 9.6 \text{ in} or 244 \text{ mm} square)

    • Retains compatibility with ATX mounting holes, making case swaps easy

    • Fewer PCIe slots (typically 1-4), often sacrificing some x16 slots for smaller footprint

    • Preferred for budget, office, and compact gaming PCs where space and cost are considerations

  • ITX Family (Information Technology eXtended)- Mini-ITX (170 \text{ mm} \times 170 \text{ mm} or 6.7 \text{ in} \times 6.7 \text{ in})

    • One full-length PCIe x16 slot, making it ideal for SFF (small form factor) builds like HTPCs (Home Theater PCs) or compact gaming rigs

    • Highly popular for minimalist and space-constrained setups

    • Nano-ITX (120 \text{ mm} \times 120 \text{ mm}), Pico-ITX (100 \text{ mm} \times 72 \text{ mm}), Mobile-ITX (75 \text{ mm} \times 45 \text{ mm})

    • Progressively smaller; primarily designed for embedded systems, often featuring soldered-on CPUs and RAM to reduce physical size and power consumption; commonly found in industrial kiosks, IoT (Internet of Things) devices, and automotive applications

System-Board Architecture

  • Buses
    – Traditional data highways measured by their width (bits) and speed (Hz or MT/s)- Front-Side Bus (FSB) → Historically connected the CPU to the Northbridge (or Memory Controller Hub), dictating the speed of communication with RAM and integrated graphics. Largely deprecated.

    • Back-Side Bus (BSB) → Historically connected the CPU to its L2/L3 cache (if external to the CPU die). Also largely deprecated.

    • Modern CPUs integrate the memory controller directly onto the CPU die, shifting to point-to-point links (e.g., Intel QuickPath Interconnect (QPI), Intel Ultra Path Interconnect (UPI) for servers, AMD Infinity Fabric) for high-speed, direct communication between CPU, memory, and other components, bypassing the traditional bus bottleneck.

  • Chipset

    • The data flow management unit, essentially the “traffic cop” of the motherboard.

    • Pre-2010: Split into Northbridge (Memory Controller Hub or MCH) and Southbridge (I/O Controller Hub or ICH).

      • Northbridge: Handled high-speed components like CPU, RAM, and PCIe graphics cards.

      • Southbridge: Managed slower I/O functions like USB, SATA, LAN, audio, and legacy PCI slots.

    • Current: Functionality integrated into a single-chip solution such as the Platform Controller Hub (Intel PCH) or AMD Promontory series (B550, X570, etc.). This single chip now manages most I/O, storage, and peripheral connections directly, with PCIe lanes often configurable by the CPU itself.

    • Determines key motherboard features such as overclocking support, total available PCIe lane count and generation, supported SATA/USB versions and ports, and advanced features like RAID configuration capabilities.

  • Expansion Slots

    • PCI (Peripheral Component Interconnect) (legacy) – A parallel bus operating at 33 \text{ MHz} or 66 \text{ MHz}, with 32-bit or 64-bit width. Provided about 133 \text{ MB/s} or 266 \text{ MB/s} bandwidth. Used for older expansion cards like sound cards, network cards, and modems.

    • PCIe (PCI Express) (current standard) – A high-speed serial interface that uses point-to-point connections. Measured in lanes (x1, x4, x8, x16) and generations (Gen1, Gen2, Gen3, Gen4, Gen5).

      • Each PCIe lane (x1) in Gen3 delivers approximately 985 \text{ MB/s} (nearly 1 \text{ GB/s} in each direction).

      • Bandwidth scales linearly with lane count: x4 offers \approx 4 \text{ GB/s}, x16 offers \approx 16 \text{ GB/s} (Gen3).

      • x1, x4, x8, x16 represent physical slot sizes. A smaller card (e.g., x1) can fit into a larger slot (e.g., x16) and will operate at its maximum lanes. However, a larger card cannot fit into a smaller physical slot.

      • Electrically backward compatible: a PCIe Gen4 card will work in a Gen3 slot, but at Gen3 speeds.

      • High-performance GPUs are typically installed in x16 slots to maximize bandwidth.

      • NVMe (Non-Volatile Memory Express) add-in cards (AIC) for high-speed SSDs usually utilize x4 PCIe lanes.

    • Riser Cards – Specialty cards used to physically rotate expansion slots (e.g., 90^{\circ} or 180^{\circ}) or extend PCIe lanes from the motherboard to accommodate space constraints, commonly found in 1U servers (horizontal cards) or compact SFF cases (vertical GPU mounts).

Memory Slots & Caches

  • DIMM slots (Dual In-line Memory Module) for desktop computers vs. SODIMM (Small Outline Dual In-line Memory Module) for laptops and SFF PCs.

    • Each DDR generation (DDR3, DDR4, DDR5) has uniquely positioned notches (keys) on the modules to prevent incorrect insertion into incompatible slots. This ensures proper voltage and pin alignment.

  • Cache hierarchy

    • CPU caches are small, high-speed memory buffers that store frequently accessed data, dramatically reducing the time it takes for the CPU to retrieve information from main RAM.

    • L1 Cache: The fastest and smallest cache, typically per-core. Usually split into instruction and data cache. Sizes are generally less than 128 \text{ kB} per core.

    • L2 Cache: Larger than L1, can be per-core or shared between a few cores. Provides a second level of fast access, usually a few MB in size.

    • L3 Cache: The largest and slowest of the CPU caches, but still significantly faster than main RAM. It is typically shared across all CPU cores and can range from tens of MB up to hundreds of MB. Its purpose is to lower latency to main RAM by storing data that might be used by any core.

CPU Sockets & Families

  • Intel

    • LGA (Land Grid Array) sockets use pins on the motherboard socket that make contact with pads on the CPU.

    • LGA 1200: Used for 10th and 11th Gen Intel Core processors (e.g., Comet Lake, Rocket Lake).

    • LGA 1700: Current mainstream desktop socket for 12th/13th/14th Gen Intel Core processors (e.g., Alder Lake, Raptor Lake, Meteor Lake).

    • Server sockets: LGA 2066 (High-End Desktop/Workstation), LGA 4189 (Intel Xeon Scalable processors, e.g., Ice Lake-SP).

  • AMD

    • PGA (Pin Grid Array) sockets historically used pins on the CPU that insert into holes on the motherboard socket (e.g., AM4).

    • AM4: PGA socket used for Ryzen 1000 through 5000 series desktop processors. Highly versatile and long-lived platform.

    • AM5: Current mainstream desktop LGA socket for Ryzen 7000 series and newer (DDR5 platforms only). Adopted LGA design similar to Intel.

    • TR4/sTRX4: LGA sockets specifically designed for high-end AMD Threadripper workstation processors, supporting many cores and high memory bandwidth.

  • Mobile & Embedded

    • BGA (Ball Grid Array) packages: CPUs are soldered directly onto the motherboard. This packaging is compact and robust, reducing thickness and improving thermal contact, but makes the CPU non-replaceable and non-upgradable. Common in laptops, tablets, and embedded systems.

  • Multi-socket Boards

    • Enterprise-grade workstations and servers often feature motherboards with 2, 4, or even 8 physical CPU sockets.

    • Require processors with matched steppings (identical production revisions) and specialized interconnects (Intel QPI/UPI or AMD InfinityFabric) for high-speed communication between CPUs and shared memory pools.

Power Connectors

  • 24-pin ATX – The primary power connector that supplies power to the motherboard logic, chipset, expansion slots, and onboard peripherals. It ensures stable operation for the entire board.

  • 4/8-pin EPS 12V – Provides dedicated, isolated 12 \text{ V} power specifically for the CPU's Voltage Regulator Modules (VRMs). This ensures clean, stable power delivery to the CPU, crucial for high performance and overclocking.

  • PCIe 6/8-pin – Supplemental power connectors for high-power graphics cards. A 6-pin connector provides up to 75 \text{ W}, while an 8-pin adds two extra ground lines to provide up to 150 \text{ W} per connector. Combined with the 75 \text{ W} from the PCIe x16 slot, powerful GPUs can draw significant wattage.

Storage & Peripheral Connectors

  • IDE/PATA (Integrated Drive Electronics/Parallel Advanced Technology Attachment) – A legacy 40-pin ribbon cable interface for storage devices. Max theoretical throughput was \approx 133 \text{ MB/s}. Primarily used for older hard drives and optical drives. Supports master/slave configuration.

  • SATA (Serial Advanced Technology Attachment) – Current standard 7-pin data cable for HDDs, SSDs, and optical drives.

    • SATA I: 1.5 \text{ Gb/s} (approx. 150 \text{ MB/s})

    • SATA II: 3 \text{ Gb/s} (approx. 300 \text{ MB/s})

    • SATA III: Up to 6 \text{ Gb/s} (approx. 600 \text{ MB/s}). Widely used.

  • eSATA (external SATA) – Shielded external version of SATA, designed for hot-swappable external drives. Offers the same speed as internal SATA, providing direct SATA performance without USB overhead.

  • M.2 (Next Generation Form Factor)

    • A versatile slot for SSDs (NVMe and SATA), Wi-Fi cards, and other peripherals.

    • Key M: Designed for NVMe SSDs utilizing PCIe x4 lanes, offering significantly higher speeds than SATA SSDs. Typical speeds for PCIe Gen3 x4 are \approx 3.5 \text{ GB/s}, Gen4 x4 \approx 7 \text{ GB/s}.

    • Key B: Supports SATA-based M.2 SSDs or PCIe x2 SSDs, offering speeds comparable to standard SATA or about half of a PCIe x4 NVMe drive.

    • M.2 drives come in various standardized sizes: e.g., 2230, 2242, 2260, 2280, 22110 (width 22 mm Ă— length 30-110 mm). 2280 is the most common for consumer SSDs.

  • Headers (Connectors for front-panel I/O)

    • Front-panel header: Connects to the case's power button, reset button, HDD activity LED, and power LED.

    • USB 2.0 header: 9-pin connector for two USB 2.0 ports (480 \text{ Mbps}).

    • USB 3.0/3.1 Gen1 header: 19-pin connector for two USB 3.0/3.1 Gen1 ports (5 \text{ Gbps}).

    • USB 3.1 Gen2/USB 3.2 Gen2x1 Type-C header: Internal connector for front-panel USB-C ports (10 \text{ Gbps}).

    • HD-Audio header: For front-panel audio jacks (headphone/microphone).

    • RGB/ARGB headers: For connecting RGB LED strips and fans for lighting control.

BIOS, UEFI & POST

  • Firmware Roles

    • BIOS (Basic Input/Output System) / UEFI (Unified Extensible Firmware Interface): Low-level software stored on a non-volatile chip (usually Flash memory) on the motherboard.

    • Initialize hardware (Power-On Self-Test or POST): A diagnostic sequence that checks essential hardware components (CPU, memory, graphics card) at startup. If an error is detected, it may generate beeps or display error codes.

    • Expose configuration interface (CMOS Setup utility): A text-based or graphical interface accessed during boot (e.g., by pressing DEL or F2) to configure hardware settings, boot order, and system clock.

    • Hand bootloader to OS: After successful POST, the firmware locates the bootable device (based on Boot Device Priority settings) and loads the operating system's bootloader.

  • UEFI Enhancements (over traditional BIOS)

    • Modern graphical user interface (GUI) with mouse support, offering a more intuitive configuration experience.

    • Support for GPT (GUID Partition Table) disks, allowing boot partitions larger than 2 \text{ TB} (traditional MBR is limited to 2 \text{ TB} and 4 primary partitions).

    • Integrated network stack: Allows for network booting (PXE) and remote firmware updates directly from the UEFI environment.

    • Secure Boot: A security feature that checks the digital signature of bootloaders and operating system components to ensure they are trusted and untampered, preventing rootkits and other malware from loading during startup. Requires an operating system that supports Secure Boot (e.g., Windows 8/10/11).

    • TPM integration: Tightly integrated with the Trusted Platform Module (discussed later) for hardware-backed keys, enhancing security for features like BitLocker drive encryption.

    • CSM (Compatibility Support Module): A UEFI feature that allows emulating a traditional BIOS environment, enabling compatibility with older operating systems or graphics cards that do not support UEFI native boot.

    • USB Permissions: Allows disabling unused USB ports in the firmware to harden kiosk PCs or sensitive systems against unauthorized data transfer or device connections.

  • CMOS & Battery

    • CMOS (Complementary Metal-Oxide-Semiconductor): A small, low-power memory chip on the motherboard that stores BIOS/UEFI settings (like date, time, boot order, hardware configurations).

    • Requires a small coin cell battery (typically a \,3 \text{ V}\, CR2032 lithium battery) to retain these settings and the system clock when the computer is unplugged from AC power.

    • Signs of battery failure: System clock resetting to default (e.g., January 1st, 2000),